The present disclosure relates to vehicle airbag systems.
Conventionally, an airbag module has been mounted in a vehicle's instrument panel above a steering member extending in the vehicle's width direction, and an airbag is deployed in front of an occupant in a passenger seat in the event of impact to the vehicle. The airbag module includes an airbag accommodated in a case and a gas generator. To increase the workability of checking and changing these components, it is preferable to design the airbag systems such that the airbag module can be easily mounted and removed.
An example vehicle airbag system designed from the above aspect is disclosed in Japanese Patent No. 4617766. In this example, a lower portion of the airbag module is supported on the steering member, and a front portion and a back portion of the airbag module are held on front and back support portions which protrude downward from the instrument panel, by hook members. Specifically, a bracket protruding downward from the case of the airbag module is provided, and this bracket is fastened to a bracket of the steering member with a bolt and a nut. The hook member on the front side is welded to a front surface of the case, and is hooked into a hole formed in the front support portion of the instrument panel. The hook member on the back side is fastened to a base bracket welded to a back surface of the case with a bolt and a nut, and is hooked into a hole formed in the back support portion of the instrument panel.
In this example, to remove the airbag module from the instrument panel, the back hook member and the back surface of the case are unfastened, and the back hook member is detached from the back support portion of the instrument panel. Then, the bracket at the lower portion of the case and the bracket of the steering member are unfastened. As a result, the hook member on the front surface of the case can be detached from the front support portion of the instrument panel, thereby making it possible to remove the airbag module.
The Japanese Patent No. 4617766 also discloses an impact absorber provided to the case of the airbag module and the base bracket, to allow smooth deformation of the case and the base bracket in the event when an impact load is applied to the instrument panel from above.
According to the above airbag system, in the event of impact to a vehicle, such as frontal collisions, a sensor (not shown) detects the impact, and the gas generator operates to inject gas into the airbag accommodated in the case. The gas inflates the folded airbag and causes airbag deployment. Due to this deployment pressure, a cleavage lid formed in the upper wall of the instrument panel is torn open, and the airbag expands in the vehicle.
In the airbag deployment, the airbag case in the airbag module is deformed to expand to the back side due to the airbag deployment pressure. If this deformation is large, it may cause delay in the airbag deployment (i.e., the airbag does not deploy immediately), and the deployment performance of the airbag is reduced. A structural bead may be provided to the wall of the airbag case to increase the stiffness of the airbag case. However, the unevenness of the wall of the airbag case formed by the structural bead may cause a disadvantage to the airbag deployment.